This invention relates to a radio communication system for simultaneous telecommunication between radio stations.
So-called simultaneous telecommunication referring to repetition of automatic alternate transmission and reception of aural information between radio stations has not been realized yet in the field of radio communications for the reasons described below. While the desired simultaneous telecommunication can be realized theoretically when a time division pulse signal of high frequency is utilized for the transmission and reception of an aural signal, utilization of such a high frequency infringes the Radio Law and is therefore impossible as a matter of fact. Although utilization of a time division pulse signal of low frequency does not infringe the Radio Law, intelligibility of reproduced aural information is too bad to be used for practical applications.
The inventors have now provided simultaneous telecommunication between a calling station and a called station in which a low frequency, which does not in any way infringe the Radio Law, can be used for time division transmission and reception of aural signals and which ensures intelligibility of reproduced aural information. The inventors have found that the desired simultaneous telecommunication can be achieved by subjecting an aural signal to time division by a low frequency in a calling station, compressing the time-divided aural signal with respect to the time axis, transmitting the compressed aural signal to a called station, expanding this compressed aural signal with respect to the time axis in the called station for reproducing the original aural signal originated in the calling station, and similarly compressing an aural signal in the called station for the purpose of automatic alternate transmission and reception of aural information between the stations.